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Wednesday, November 15, 2006

Climate change: Not unusual, not unnatural and not unprecedented

CO2 Science has an article that once more exposes the myth that current global warming surpasses anything ever seen before - and that man is the cause. It also exposes the way anthropogenic climate change supporters distort their findings to support their mythical cause.

In their recent paper in The Holocene, Joerin et al. (2006) say "the exceptional trend of warming during the twentieth century in relation to the last 1000 years highlights the importance of assessing natural variability of climate change." Why? The only reason that comes to our minds is to be able to determine, by comparison, if there is anything unusual, unnatural, or unprecedented about the past century's increase in temperature, which is the way in which the world's climate alarmists typically describe 20th-century global warming.

So what did they find?

First of all, Joerin et al. report discovering that "alpine glacier recessions occurred at least 12 times during the Holocene," once again demonstrating the reality of the millennial-scale oscillation of climate that has reverberated throughout glacial and interglacial periods alike as far back in time as scientists have searched for the phenomenon (see Climate Oscillations (Millennial Variability) in our Subject Index). As a result of this finding, it is clear that 20th-century global warming was not unusual. It is was merely the latest example of what has been the norm throughout hundreds of thousands of years.

So there you go - global warming is not unusual. But we knew that already, didn't we. Didn't we?

Second, they determined that glacier recessions have been decreasing in frequency since approximately 7000 years ago, and especially since 3200 years ago, "culminating in the maximum glacier extent of the 'Little Ice Age'." Consequently, the significant warming of the 20th century cannot be considered strange, since it represents a climatic rebounding from the coldest period of the current interglacial, which interglacial just happens to be the coldest of the last five interglacials (Petit et al., 1999). And when the earth has been that cold for a few centuries, it is not unnatural to expect that, once started, warming would be rather significant. (My emphasis).

Of course it's not unnatural. If you have a cold winter, then it is going to warm up more and faster as it approaches spring - and if that cold winter is followed by a warm winter, then the trend will be increased even more. Does that make it unnatural? Of course not - unless you're a Canutist.

Third, the last of the major glacier recessions in the Swiss Alps occurred between about 1400 and 1200 years ago, according to Joerin et al.'s data, but between 1200 and 800 years ago, according to the data of Holzhauser et al. (2005) for the Great Aletsch Glacier. Of this discrepancy, Joerin et al. say that given the uncertainty of the radiocarbon dates, the two records need not be considered inconsistent with each other. What is more, their presentation of the Great Aletsch Glacier data indicates that the glacier's length at about AD 1000 - when there was fully 100 ppm less CO2 in the air than there is today - was just slightly less than its length in 2002, suggesting that the peak temperature of the Medieval Warm Period likely was slightly higher than the peak temperature of the 20th century. Consequently, 20th-century warming has likely not been unprecedented over the past millennium. (My emphasis).

Canutists don't believe the Medieval Warm Period existed. At least they would prefer if it didn't so they spend all their time denying it even though there is plenty of historical evidence to suggest that not only did it exist but it was actually significantly warmer than today - despite the absence of 4x4s and coal fired power stations.

In conclusion, it is our feeling that being neither unusual, unnatural nor unprecedented, there is no compelling reason to attribute 20th-century global warming to anthropogenic CO2 emissions. The temperature increase of the past hundred or so years has been simply a run-of-the-mill consequence of cyclically-recurring forces of nature that have manifested themselves again and again throughout earth's history at millennial-scale intervals.

This won't stop the Environazis or the Canutists. They won't let little things like facts and evidence get in their way. As I said at the start, the CO2 chaps expose the way supporters of man-made climate change distort their own findings to promote their point of view. How else can you explain why the authors of this research say "the exceptional trend of warming during the twentieth century in relation to the last 1000 years highlights the importance of assessing natural variability of climate change" when their own report suggests that it is far from exceptional?